1. Field of the Invention
The present invention relates to the constituent parts of a coupling between the load and rotor of a single-phase synchronous motor which transmits rotation to the load, such as the coupling between the rotor and the impeller of a drain pump, in order to eliminate noise and vibrations.
2. Prior Art
ES-2053372 (n.sup.o P9200335) describes a coupling of a drain pump impeller to the rotor shaft of its synchronous motor with a permanent magnetic rotor. The pump impeller has an internal cavity where the rotor shaft is coupled, sealed with a cap. At one end the rotor shaft for coupling to the impeller has an integral coupling cam, fitted with a radial drive catch, which moves back and forth in a free travel inside the impeller chamber for off-load pump starting. The coupling for rotation transmission is realized by means of a radial stopper integral with the impeller, and in its chamber it occupies a circular sector, which has a restricted angle in order to provide the rotor shaft and its drive catch with sufficient angle of free travel for starting the motor by vibration in either of the two directions of rotation. The drive catch engages afterwards with the impeller stopper and makes it turn at synchronous speed. To cushion the impacts of the drive catch against the impeller stopper in both directions of rotation the latter has a cushioning piece inserted made of elastomer material which protrudes laterally from both ends of the stopper in order to absorb the impacts and thereby reduce noise and vibration. This coupling solution has the drawback of being short-lived due to fatigue breakage of the cushioning stopper as a result of the heavy impacts against it, which cannot be remedied by making it thicker because said free angular play should not be reduced.
EP-514272 discloses a drain pump impeller coupling solution for transmitting the rotation of its synchronous motor in which a stopper integral with the impeller has cushioning devices formed or attached, consisting of springs in the form of flexible tabs on either side of the stopper. This solution also has a service life problem due to fatigue.
EP-474004 discloses a solution for the coupling of the rotor shaft to the rotor of a synchronous motor for transmitting rotation, which has an internal rubber ring attached to the rotor with two integrated stop lugs that impact against a radial cam drive catch attached to the rotor shaft, in a respective direction of rotation of the rotor, and it is an attached part made entirely of rubber affixed to the impeller. This solution also has a service life problem due to fatigue in the rubber cushioning ring attached to the impeller.